(purple sulphur bacteria; order Rhodospirillales)
A family of anaerobic, anoxygenic, photosynthetic bacteria that can use sulphur, sulphide, or other reduced inorganic sulphur compounds as sources of reduction for photosynthesis. Most species accumulate granules of sulphur inside their cells. Many species are motile with flagella. Cells are spherical, spiral, ovoid or rod-shaped, and range in colour from pinkish-red to orange-brown. Cells may occur singly or as aggregates embedded in slime. Photosynthetic pigments are attached to membranes which are continuous with the cytoplasmic membrane. There are several genera, with many species; they are found in sulphide-rich, anaerobic, aquatic environments, often forming pink to purple-red blooms.
Subjects: Plant Sciences and Forestry.